JP2007198753A - Water quantity measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure the water quantity of an ever-changing a small quantity of generated water as to performance evaluation on a fuel cell. <P>SOLUTION: By this water quantity measuring instrument 10 comprising a nozzle 20 for dropping generated water onto a substantially cylindrical rotor 30 rotatively driven by a motor 50 rotating at a certain rotational speed under a control part 90, the generated water's hitting on the rotor 30 makes it possible to measure the water quantity based on a detection result of a torque detector 80 for detecting load fluctuation of the motor 50 and on data of a storage part 95 for therein storing a relation between the load fluctuation of the motor 50 and the water quantity. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a water amount measuring device, and more particularly to a water amount measuring device that measures the amount of produced water in performance evaluation of a polymer electrolyte fuel cell.

  In recent years, various research and development related to fuel cells have been conducted. In particular, in the automobile industry, research and development are actively conducted toward the practical application of a polymer electrolyte fuel cell to be mounted on a motor-driven electric vehicle that can be an alternative to an internal combustion engine vehicle in the future.

  A polymer electrolyte fuel cell (fuel cell) has a membrane-electrode assembly (MEA) in which a fuel electrode (anode), a polymer electrolyte membrane, and an air electrode (cathode) are sequentially laminated. It has a structure that is sandwiched between sheets of separators. Since one battery is constituted by this structure, this structure is generally called a cell. The anode and the cathode have an electrode catalyst layer and a gas diffusion layer, the electrode catalyst layer faces the polymer electrolyte membrane side, and the gas diffusion layer faces the separator. Each separator forms a fluid path for supplying hydrogen gas to the anode and oxygen gas to the cathode.

  The power generation by the electrochemical reaction of the fuel cell will be described. In the anode gas diffusion layer, hydrogen gas supplied through the separator is diffused toward the anode electrode catalyst layer. In the anode electrode catalyst layer, hydrogen gas is dissociated into hydrogen ions and electrons according to the following formula by the catalytic action of the anode.

H ₂ → 2H ⁺ + 2e ⁻

  Hydrogen ions generated by the catalytic action of the anode permeate the polymer electrolyte membrane having proton conductivity and are sent to the cathode. Electrons generated by the catalytic action of the anode are sent to the cathode through an external circuit.

  On the other hand, in the cathode, oxygen gas supplied to the cathode gas diffusion layer through the separator is diffused toward the cathode electrode catalyst layer. In the cathode electrode catalyst layer, hydrogen ions that have permeated the polymer electrolyte membrane and electrons supplied through an external circuit react with oxygen by the catalysis of canodes to generate water according to the following equation.

2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O

  The series of electrochemical reactions in the MEA enables the cell to supply power to the outside. Note that the fuel cell system that is normally used is configured to obtain a desired electromotive force as a cell stack in which a large number of cells are stacked in the stacking direction.

  Fuel cells have different electrochemical reaction behavior and performance such as power generation capacity depending on usage conditions (for example, gas amount, gas pressure, temperature, MEA material). In basic research, it is important to evaluate the performance under such usage conditions for the practical application of fuel cells. Among them, measuring the amount of water produced according to the electrochemical reaction is one effective means for grasping the behavior of the electrochemical reaction of the fuel cell.

  As a conventional technique, a method for measuring the generated water of a fuel cell accumulates the generated water discharged from the fuel cell in a container, and measures the accumulated amount of water every predetermined time. And the behavior of the electrochemical reaction of the fuel cell was estimated from the measured amount of generated water. Further, in the size of a fuel cell that is put into practical use, the amount of generated water is about several L / min, and the amount of generated water can be measured with a normal flow meter or the like.

  Patent Document 1 discloses a technique for measuring the amount of water generated by a water meter in a fuel cell power generator, measuring the time required to accumulate a predetermined amount, and determining the flow rate per unit time.

  In Patent Document 2, in a flow meter, a rotating body that rotates at a constant rotational speed under the control of a motor captures a liquid and gives energy at the same rotational speed. A technique for measuring the flow rate of a liquid based on (power consumption) is disclosed.

JP-A-8-167423 JP-A-7-209055

In the performance evaluation of a fuel cell, a basic configuration such as selection of cell constituent materials may be evaluated. At this time, the fuel cell used for performance evaluation is a prototype small cell having a cell size of about several tens of cm ² . In this small cell, the amount of generated water is about several mL / min, and the amount of generated water is small. For this reason, a general flow meter cannot be used, and the amount of water accumulated over a relatively long time is measured. Therefore, it becomes difficult to estimate the behavior of the electrochemical reaction of the fuel cell from the change over time in the amount of produced water, which is the purpose of the performance evaluation of the fuel cell.

  An object of the present invention is to provide a water amount measuring device capable of measuring a small amount of water that changes every moment with a simple structure in the performance evaluation of a fuel cell.

  In order to solve the above-described problems, a water amount measuring device of the present invention includes a substantially cylindrical rotator, a motor that rotationally drives the rotator, a control unit that rotates the motor at a constant rotational speed, and the motor. A detector that detects fluctuations in the load applied to the rotator, and a dropping means that drops water as a measurement object toward the rotator, and measures the amount of water based on the detection result of the detector. Can do.

  In addition, the water amount measuring device of the present invention has a storage unit that stores a calibration curve indicating a relationship between a load variation applied to the motor and a water amount, and the detection is performed based on the calibration curve stored in the storage unit. It is preferable to measure the amount of water from the detection result of the vessel.

  Furthermore, it is preferable that the water amount measuring device of the present invention measures the amount of generated water in the performance evaluation of the fuel cell.

  According to the water amount measuring apparatus of the present invention, it is possible to measure a small amount of water that changes every moment with a simple structure.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In the present embodiment, as an example, an apparatus for measuring the amount of generated water in the performance evaluation of a fuel cell will be described. However, the present invention is not limited to this embodiment, and can be used as an apparatus for measuring the flow rate of liquid.

  FIG. 1 is a configuration diagram showing a schematic configuration of a water amount measuring apparatus according to an embodiment of the present invention. The water amount measuring apparatus 10 includes a substantially cylindrical rotator 30 and a motor 50 that rotationally drives the rotator 30. A rotator 30 is attached to an output shaft 60 that is a rotation shaft of the motor 50. The output shaft 60 is supported by bearings 40 on both sides of the rotator 30. Thereby, the motor 50 can generate a rotational torque based on the supplied electric power, and can rotate the rotator 30 via the output shaft 60.

  The rotator 30 has a substantially cylindrical shape, and the substantially cylindrical tube portion 32 has a shape for receiving a water flow. Accordingly, when the generated water hits the cylindrical portion 32 of the rotating rotator 30, the rotator 30 gives kinetic energy to the generated water. In other words, the rotator 30 receives a load from the generated water. Therefore, when the amount of generated water varies, the load received by the rotator 30 varies, and the load of the motor 50 that rotates the rotator 30 varies. As a result, there is a correlation between the fluctuation of the water amount and the fluctuation of the motor load, and the amount of water hitting the rotator 30 can be derived by detecting the fluctuation of the motor load.

  As for the shape of the cylindrical part 32 of the rotator 30, for example, the cylindrical part 32 is an impeller, and each blade of the impeller may protrude from the outer peripheral part, or each blade is sandwiched by the wall surface part 34. You may do it. In addition, the shape of the cylindrical portion 32 of the rotator 30 may be a shape in which grooves in a direction parallel to the rotation axis of the rotator 30 are formed on the surface of the cylindrical portion 32, or a shape in which a number of irregularities are simply formed.

  Above the rotator 30, there is a nozzle 20 that drops the produced water. The position of the nozzle 20 with respect to the rotator 30 is a position where a load can be applied to the rotator 30 by the generated water that falls. That is, the position where the falling generated water hits the rotator 30 is a position where the rotating direction of the rotator 30 and the direction in which the generated water falls are opposed to each other even at the top of the rotator 30. , Up to −90 degrees with respect to the rotation direction of the rotator 30), or a section in between. When the generated water hits the top of the rotator 30, a portion (for example, a blade of an impeller) on which the rotator 30 hits moves horizontally with respect to the generated water that has fallen. Therefore, horizontal kinetic energy is given to the generated water. In the case where the rotation direction of the rotator 30 and the direction in which the generated water falls are opposite to each other, a portion (for example, a blade of an impeller) on which the rotator hits is moving upward with respect to the dropped generated water. Thus, vertical kinetic energy is given to the generated water. As a result, the rotator 30 receives a load from the generated water. Further, the position where the generated water hits the rotator 30 may be a section from the top of the rotator 30 to 90 degrees with respect to the rotation direction of the rotator 30 when the top of the rotator 30 is 0 degree. In this case, since the rotation direction of the rotator 30 and the falling direction of the generated water follow, the load received by the rotator 30 decreases as the amount of water increases.

  The generated water discharged from the discharge pipe 2 of the fuel cell 1 is supplied to the nozzle 20. Here, the fuel cell 1 discharges the gas (oxygen gas) that has not reacted in the electrochemical reaction with the generated water. Furthermore, since the fuel cell 1 is at a high temperature due to an electrochemical reaction, a part of the generated water is vaporized to become water vapor. Therefore, it is effective to provide the gas-liquid separator 3 in the middle of the discharge pipe 2. The gas-liquid separator 3 lowers the oxygen gas discharged from the fuel cell 1 to a certain temperature by the cooler 4 to liquefy the water vapor. As a result, the amount of water that escapes as water vapor can be made almost zero or a constant amount, and the generated water can be supplied to the nozzle 20.

  The water amount measuring apparatus 10 includes a control unit 90 that controls the motor 50 and calculates the water amount. The motor 50 is provided with a rotation detector 70 that detects the rotation state, and sends the detection result to the control unit 90. Based on the detection result of the rotation detector 70, the control unit 90 controls the electric power supplied to the motor 50 so as to rotate the motor 50 at a constant rotational speed.

  A torque detector 80 for detecting a torque deviation is disposed on the output shaft 60, and the detection result is sent to the control unit 90. The control unit 90 calculates the amount of water based on the detection result of the torque detector 80 and the data from the storage unit 95. That is, the relationship between the load fluctuation of the motor 50 and the amount of water is examined in advance, and the calibration curve obtained as a result is stored in the storage unit 95 as a table. In the present embodiment, the load fluctuation of the motor 50 is a torque deviation of the detection result of the torque detector 80. This load fluctuation of the motor 50 also appears in the current value supplied to the motor 50. On the other hand, the control unit 90 includes a current detector in order to control the supplied power so that the rotation speed of the motor 50 is constant. Therefore, the load fluctuation of the motor 50 can use the detection result of this current detector. Further, a control amount for keeping the rotation speed of the motor 50 constant may be a load fluctuation of the motor 50.

  Next, the operation of the water volume measuring device 10 will be described. The motor 50 rotates by generating rotational torque by the electric power supplied from the control unit 90. Accordingly, the coaxial rotator 30 also rotates. The control unit 90 controls the power supplied to the motor 50 based on the detection result from the rotation detector 70 in order to rotate the motor 50 at a set constant rotation speed. As a result, the motor 50 can always rotate at a set constant rotation speed.

  Generated water and exhaust gas are discharged from the fuel cell 1 for performance evaluation by an electrochemical reaction. The gas-liquid separation device 3 liquefies the produced water that has become steam by lowering the exhaust gas to a certain temperature by the cooler 4. The generated water separated by the gas-liquid separator 3 is supplied to the nozzle 20. The generated water falling from the nozzle 20 hits the rotator 30. At this time, the rotator 30 receives a load from the generated water. When the rotator 30 receives a load, the motor is loaded, and the rotation speed changes. The rotation detector 70 detects a change in the rotation speed and sends the detection result to the control unit 90. The control unit 90 controls the power supplied to the motor 50 so that the set number of rotations is achieved. The torque detector 80 detects that the torque has changed, and sends the detection result to the control unit 90. The control unit 90 compares the detection result with the data in the storage unit 95 to calculate the amount of water.

  As described above, the water amount measuring device 10 can measure a small amount of water that changes every moment in the performance evaluation of the fuel cell.

  It is preferable to reduce the weight by configuring the rotator 30 with a lightweight material such as plastic. In addition, the weight-reduced rotator 30 is easily affected by rotation even with a small amount of generated water.

It is a block diagram which shows this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Fuel cell, 2 discharge line, 3 gas-liquid separator, 4 cooler, 10 water quantity measuring device, 20 nozzle, 30 rotator, 32 cylinder part, 34 wall surface part, 40 bearing, 50 motor, 60 output shaft, 70 Rotation detector, 80 torque detector, 90 control unit, 95 storage unit.

Claims (3)

In the water volume measuring device,
A substantially cylindrical rotator;
A motor for rotating the rotator,
A control unit for rotating the motor at a constant rotational speed;
A detector for detecting a change in load applied to the motor;
To this rotator, dropping means for dropping the water to be measured,
Have
A water volume measuring device capable of measuring the water volume based on the detection result of the detector. In the water amount measuring device according to claim 1,
A storage unit for storing a calibration curve indicating the relationship between the load variation applied to the motor and the amount of water;
A water amount measuring device capable of measuring a water amount from a detection result of the detector based on a calibration curve stored in the storage unit.   The water amount measuring device according to claim 2 is a water amount measuring device that measures the amount of generated water in performance evaluation of a fuel cell.

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